With the development of communication technologies in recent years, an inter-vehicle communication system which performs communication between moving vehicles by using in-vehicle communication devices mounted on the vehicles, and a road-to-vehicle communication system which performs communication between a vehicle and a roadside communication device installed at the roadside of a road, an interchange, or the like, have become widely used.
Patent Document 1 (JP2005-12522A) discloses an inter-vehicle communication method which aims at suppressing an increase in redundant traffic due to inter-vehicle communication, and at enabling a radio band to be effectively used in the vehicle communication.
Patent Document 1 discloses a method in which, when communication is performed by successively relaying transmission information between vehicles, a communication source determines, as a relay vehicle, a surrounding vehicle that is located on a branch road and that is located furthest from the vehicle of the communication source itself, on the basis of the position information of the surrounding vehicles and the map information.
Patent Document 1: JP2005-12522A (page 4 to 6)